Wireless systems currently in use are mainly voice services based. Supplemental services such as short message service (SMS), multimedia messaging service (MMS), instant messaging service (IMS) and the like have been deployed over wireless systems and generate significant revenues for the operators. This is complicated by the fact that these services are closely tied to specific technologies and network infrastructure and users may not be able to reach these services by way of another wireless access technology other than the one supported by the user's terminal.
The integration of WLAN and other such networks into existing wireless (such as cellular) networks makes delivery to multiple interfaces advantageous. The existing wireless networks include general packet radio service (GPRS), universal mobile telecommunication system (UMTS), code division multiple access 2000 (CDMA 2000) to name just a few, together with the variety of wireless terminals that can support such technologies. The multiple networks make it advantageous to provide for independent delivery of such services to wireless terminals capable to supporting multiple radio interfaces and network infrastructures.
The IEEE 802.11 communications protocol allows a client to roam among multiple access points that may be operating on the same or separate channels. IEEE 802.11 communications are generally effected through wireless LAN access points (APs), which are typically single standalone units, but can include networks with multiple APs which provide a roaming function. To support the roaming function, each access point typically transmits a beacon signal every 100 ms. A roaming station (STA) uses the beacon to gauge the strength of its existing access point connection. If the STA senses a weak signal, the roaming STA can implement the reassociation service to connect to an access point emitting a stronger signal. In addition to IEEE 802.11, there are other “802” series protocols, such as IEEE 802.16, IEEE 802.20 as well as similar protocols which do not follow an IEEE “802” standard.
In multiple mode systems, a selection is made of a radio access technology (RAT) in a system which includes at least two networks having different RAT capabilities compatible with the RAT capabilities for communicating with a wireless transmit/receive unit (WTRU) having multiple RAT capabilities.
Accordingly, it is desirable to more effectively utilize the capabilities of multi-mode terminal.